1. Field of the Invention
The present invention relates to linear actuators, and more particularly, to a linear actuator capable of inducing a linear motion on a rotor using an angular velocity difference between two rotors.
2. Description of the Related Art
In general, a conventional rotating body needs a linear motor around the rotary shaft of a rotor for linear motion. This linear motor is powered via a power supply path by an external power source. However, such a conventional rotating body suffers from problems in supplying power to the linear motor positioned on the rotor.
A brush is needed to supply power to such a linear motor. However, due to brush wear and damage, the lifetime is shortened, and the waveform of a supply power becomes unstable, increasing the likelihood of noise and vibration occurring when applied to a precise device. Also, the structure using a brush adds complexity to the structure of a product and increases the cost of manufacturing.
A wireless power transmission technique has been considered. However, this wireless technique has a problem of very low transmission rate. In particular, when applied to a storage device or miniature device that is sensitive to external electric fields, the design itself is complicated, and operational efficiency can be remarkably reduced.
To solve the above-described problems, it is an object of the present invention to provide a linear actuator capable of inducing a linear motion on a rotor with a simple structure without need to mount an additional linear motor as a driving power source on the rotor.
To achieve the object of the present invention, there is provided a linear actuator using two rotors, comprising: first and second rotors connected to respective driving force sources; a linear motion unit formed on the first rotor to be linearly movable; and a driving power transmission unit which is fixed to the second rotor and engages the linear motion unit.
It is preferable that the linear motion unit is coupled to the first rotor by a linear bearing such that the linear motion unit can linearly move. It is preferable that the linear motion unit engages the driving power transmission unit and linearly moves due to a relative angular velocity difference between the first and second rotors. It is preferable that the linear motion unit is a rack, and the driving power transmission unit is a pinion. It is preferable that the first and second rotors are controlled by respective spindle motors such that the first and second rotors rotate at different velocities.
In another embodiment of the present invention, a linear actuator is provided that includes a first rotor; a second rotor, wherein said first and second rotors are connected to respective driving force sources; a linear motion unit formed on the first rotor to be linearly movable; and a driving power transmission unit which is fixed to the second rotor and engages the linear motion unit, wherein the linear motion unit moves linearly by engagement with the driving power transmission unit when the first and second rotor differ in angular velocity.